A San Diego hotel room tax to finance the planned expansion of the convention center is legal, a Superior Court judge ruled Thursday, but appeals are likely, setting the stage for potentially lengthy project delays.

Superior Court Judge Ronald Prager reaffirmed his earlier tentative ruling in which he concluded that under both state and local laws, a hotelier-approved room tax is a legally acceptable means for financing the $520 million expansion project.

His ruling came a day after he heard oral arguments from both the city and lawyers representing opponents of the hotel tax.

At issue was a citywide community facilities district the city formed last year so that hotel owners within the city limits could vote to enact a special property tax that would be passed onto hotel guests in the form of a 1 percent to 3 percent room surcharge. The tax was approved overwhelmingly last year in a weighted mail-ballot election that favored the city's largest hotels, based on the expected revenues they would generate.

The hotel tax is expected to generate roughly $35 million a year over 30 years to finance the bulk of the expansion project.

Prager ruled that the financing mechanism complied with all local and state laws affecting charter cities, dismissing arguments from opponents that the tax required a vote of the general electorate as opposed to the landowners. The city, Prager concluded, "has established that its definition of qualified elector was not improper."

Attorney Cory Briggs, who represents the citizens group San Diegans for Open Government, has vowed to appeal, which attorneys on both sides agree could potentially delay the expansion project for a year or more. Briggs had filed a lawsuit challenging the hotel room tax, as did citizen activist Mel Shapiro.

"An appeal will take 12 to 18 months," Briggs said. "If we have to go to the state Supreme Court, add another 12 to 18 months."

The city of San Diego had filed a legal action of its own more than a year ago seeking a confirmation of whether the hotel levy was legal because the financing plan was a "relatively untested area of the law," said City Attorney Jan Goldsmith.

"The California Constitution requires that taxes be approved by a two-thirds vote of the qualified electorate," he said in a written statement. "But, this tax was not submitted to all voters in the city. Instead, it was only submitted to hotel property owners within the city.

"...If we believed that the plan is illegal, we would not sign off. There is a big difference between illegality and lack of clarity. Now we have the clarity we sought."

The city's outside attorneys on the case have acknowledged that the expansion project cannot move forward until all litigation has ended.

"The financing structure is not going to happen until this case is over," said attorney Michael Weed, one of the private lawyers representing the city.

The expansion still faces one additional hurdle -- approval by the California Coastal Commission. A hearing on the project is expected to be scheduled for the agency's June board meeting.